This is a simple USB adapter box for the excellent Galaxy S3 & S4 Dock - CASE COMPATIBLE from BloodBlight. The adapter will fit the Samsung USB charger cable shown above (I believe this was from a Galaxy S2 before....).Print with 10% infill, 2 shells. Some slight trimming might be required with a sharp knife. Route the USB cable through the dock, insert the USB cable into the box - correct way around for your phone - and close the box with the lid. Slide the box into the dock's slot. It should sit pretty tight and require some force. if necessary secure with a drop of super glue (for mine the friction lock worked good enough so no glue was required).